JP3441695B2 - Manufacturing method of sintered oil-impregnated bearing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sintered oil-impregnated bearing which is used in a capstan motor of a VTR, a spindle motor for a disk medium of a CD-ROM, or the like and which supports a shaft over a wide rotation speed range. .

[0002]

2. Description of the Related Art Heretofore, highly accurate and inexpensive sintered oil-impregnated bearings have been widely used as bearings for VTR capstan motors and CD-ROM spindle motor bearings. Further, in recent years, as the VTRs and CD-ROMs have become more sophisticated, there has been a demand for motor bearings that can be used in a wide range of rotational speeds.

Generally, when the surface opening ratio of the bearing is increased, the supply of oil is promoted by the self-lubricating action, the oil running out in the high rotation speed region can be prevented, and the lubrication characteristics are improved.
On the other hand, if the surface aperture ratio is reduced, the escape of oil can be prevented, so that a stable oil film can be formed and the lubricating characteristics in the low rotation speed region are improved. Therefore, a bearing having a rough portion having a large surface aperture ratio and a dense portion having a small surface aperture ratio can be expected as a motor bearing that can be used in a wide rotational speed range.

A sintered oil-impregnated bearing having a rough portion and a dense portion on its inner peripheral surface is known. For example, in Japanese Unexamined Patent Publication No. 1-219108, a sintered body having a plurality of grooves on its outer peripheral surface is sintered and then sized by using a perfect circular die to obtain a pore ratio (pore area / total area). ) A bearing in which a small dense surface and a rough surface having a large pore ratio are adjacent to each other has been proposed. Further, in Japanese Unexamined Patent Publication No. 6-123313, a core rod having a roughened surface portion at a predetermined location on the outer peripheral surface is used, and the surface of the green compact is crushed by crushing the porosity of the green compact portion in contact with the roughened portion during compacting. A bearing having a small opening ratio and a sliding surface with respect to the shaft has been proposed. In addition, JP-A-11-28076
No. 6 discloses a bearing having a crushed portion having a small surface opening ratio, which is formed by shaving a convex portion formed by a groove of a center core during green compact molding when the center core is extracted. There is.

[0005]

However, in the above-mentioned conventional method, when attempting to extract the green compact having the undercut from the core rod, there were the following problems. This will be described with reference to the drawings.

FIG. 36 is a schematic sectional view showing a process for producing a green compact in a conventional method for producing a sintered oil-impregnated bearing. The raw material powder 51 is slidably fitted between an outer die 53 having an up-down direction as an axial direction, an inner die core rod 54 coaxially arranged in the die 53, and the die 53 and the core rod 54. Between the lower punch 55 and the lower punch 55 (see FIG. 36).
(A)). Then, the upper punch 56 is lowered to move the die 53.
36 and the core rod 54 are slidably fitted to each other and the raw material powder 51 is compressed under pressure to form a green compact 52 (FIG. 36).
(B)). Then, after the upper punch 56 is lifted from the die 53, the lower punch 55 is lifted to move the green compact 5 from the die 53.
2 is extracted (FIG. 36 (c)). Then, the green compact 52 is discharged and the lower punch 55 is lowered (see FIG. 36).
(D).

That is, in the conventional method, the fine porous material is moved and aggregated by the friction between the outer peripheral surface of the core rod and the inner peripheral surface of the green compact to form a large porous material. Since the surface aperture ratio may increase, it is not easy to change the surface aperture ratio according to the shape of the undercut to form the rough portion and the dense portion. Therefore, it has been difficult to obtain bearing characteristics that can accommodate a wide range of rotation speeds.

Therefore, an object of the present invention is to provide a method for manufacturing a sintered oil-impregnated bearing capable of easily changing the surface aperture ratio according to the shape of the undercut.

[0009]

In order to achieve the above object, in the molding of a green compact, after the powder is pressed in a mold, the green compact is kept pressed by an upper punch and a lower punch. Then, the core rod and the upper punch and the lower punch are synchronously moved in the axial direction to extract the green compact from the die and extract the core rod from the green compact.
As a result, a concavo-convex surface including concave groove portions and convex rib portions is formed on the inner peripheral surface of the green compact.

That is, in the manufacturing method of the present invention,
A plurality of recesses and protrusions are formed on the outer peripheral surface of the core rod coaxially arranged in the die, and raw material powder is filled between the die and the lower punch slidably fitted between the core rod and the lower punch. The punch and the upper punch are moved in the axial direction, and the raw material powder is pressure-compressed to obtain a green compact, which is characterized by maintaining the state in which the green compact is pressed by the upper punch and the lower punch. Then, the core rod and the upper punch and the lower punch are synchronously moved in the axial direction and extracted from the die to release the compressive force from the die to the green compact, and while maintaining the vertical pressure,
The core rod is pulled out from the powder compact whose inner diameter is enlarged by spring back.

According to the manufacturing method of the present invention, the compression force from the die to the green compact is released while maintaining the axially pressed state of the green compact by the upper punch and the lower punch. The springback amount of the green compact can be almost doubled as compared with the conventional case where the state where the green compact is pressed by the upper punch and the lower punch is not held. Therefore, in the method of the present invention, the core rod having the undercut can be easily extracted from the green compact. As a result, the friction between the inner peripheral surface of the green compact and the outer peripheral surface of the core rod can be reduced or eliminated, so that it is possible to prevent the fine pores from being moved and aggregated to become a large pore when the core rod is extracted. It will be possible.

Further, since the amount of undercut, that is, the amount of protrusion of the convex portion of the outer peripheral surface of the core rod can be made large, the shape of the undercut that can be applied to the inner peripheral surface of the green compact can be set and formed quite freely. be able to. This facilitates the formation of an oil passage shape in which oil is supplied and circulated according to the rotation speed range used.

Further, in the manufacturing method of the present invention, after the green compact having the above-mentioned concave and convex portions is sintered, the inner peripheral surface of the sintered body is finished into a perfect circular shape, and the inner peripheral surface is finished. It is possible to form a dense portion having a small surface aperture ratio in the convex portion and a rough portion having a larger surface aperture ratio in the concave portion. When finishing is performed using an inner diameter finishing tool, the convex portion and the concave portion are processed into a perfect circular shape due to plastic deformation. Here, due to the difference in the finishing allowance between the concave portion and the convex portion, the convex portion becomes a dense portion with a small surface aperture ratio by crushing fine pores, and oil escape can be prevented, so that a stable oil film can be formed. On the other hand, an oil passage corresponding to a rough portion having a surface opening ratio larger than that of the dense portion is formed in the concave portion and serves as an oil supply portion and an oil circulation portion.

Further, in the present invention, the springback amount can be increased as compared with the prior art, so that the protrusion amount of the convex portion on the inner peripheral surface of the green compact can be increased.
As a result, the compressive force of the inner diameter finishing tool on the convex portion at the time of finishing is increased, so that the crushing of the porous due to plastic deformation is promoted and the surface aperture ratio can be further reduced.

The sintered oil-impregnated bearing manufactured by the manufacturing method of the present invention has, on the inner peripheral surface thereof, a plurality of rough portions having a large surface opening ratio and dense portions having a surface opening ratio smaller than that of the rough portions. In addition, it has a fine pore on average as compared with the conventional one. A surface aperture ratio of 10% or less, preferably 8% or less, can be easily obtained in the dense portion. The rough portion holds a large amount of oil and supplies and circulates the oil to the dense portion when the shaft rotates, so that a stable oil film is formed in the dense portion, and the bearing can be used in a wide rotation speed range.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a schematic cross-sectional view showing a process for producing a green compact in the method for producing a sintered oil-impregnated bearing according to the first embodiment. At the time of powder filling, a die 3 having an outer straight type hollow inner surface whose axial direction is the vertical direction, an inner core rod 4 coaxially arranged on the inner surface of the die 3, and a space between the die 3 and the core rod 4. A lower punch 6 slidably fitted to the raw powder 1
Is filled in the space between the die 3 and the core rod 4 (see FIG. 1).
(A)). Next, the upper punch 5 is lowered and fitted between the die 3 and the core rod 4, and the raw material powder 1 is pressure-compressed by the upper punch 5 and the lower punch 6 to obtain a green compact 2 (FIG. 1).
(B)).

As shown in FIG. 2, the core rod 4 has an outer peripheral surface on which an undercut is formed which is an uneven surface in which a plurality of recessed grooves and projections having a predetermined width are alternately arranged. Can be used. The uneven surface of the core rod is transferred and shaped on the inner peripheral surface of the green compact when the green compact is pressed and compressed.

Then, in a state where the green compact 2 is pressed and held by the upper punch 5 and the lower punch 6, the core rod 4 and the upper punch 5 and the lower punch 6 are synchronously moved in the axial direction and extracted from the die 3. , The compression force from the die 3 to the green compact 2 is released (FIG. 1 (c)). At this time, since the green compact 2 is pressed in the axial direction by the upper punch 5 and the lower punch 6, it is almost twice as large as that in the case where it is not pressed in the axial direction.
A large springback amount of 3 to 0.5% can be obtained.
The spring back expands the inner diameter of the green compact 2 so that the core rod 4 can be easily pulled out (FIG. 1 (d)). Next, the green compact 2 is discharged and the lower punch 6 is lowered to complete the green compact manufacturing process (FIG. 1).
(E)).

The graph of FIG. 3 shows the experimental results of the relationship between the springback amount and the relative density of a green compact having no undercut. Sample 1 is
It is a green compact formed by the method of the present embodiment, and sample 2 is a green compact formed by the conventional method. The relative density is obtained by dividing the density of the green compact by the density on the assumption that the green compact has no porosity. If the relative density is large, the surface aperture ratio decreases. Relative density is 76-86%
In the range of, the sample 2 has a springback rate of about 0.2%, while the sample 1 has a springback rate of about 0.35 to 0.45%, which is almost twice as much as that of the sample 2. .

Further, the green compact 2 produced in this way
After undergoing a sintering process, is subjected to inner diameter finishing. FIG. 4 is a schematic diagram showing a finishing process, and only the bearing portion is shown in a sectional view. The pair of bearings 10a and 10b are press-fitted into a predetermined holder 16 and then fixed to a fixing jig 17. Then, by rotatably inserting the finishing tool 19 with the circumscribed surface attached to the rotator chuck portion 18 having a desired diameter into the shaft hole, the bearing 10a,
The inner peripheral surface of 10b is plastically deformed and processed into a perfect circle.
At the time of this processing, the convex portion of the inner peripheral surface of the sintered body is compressed,
A substantially circular cylindrical surface is formed.

As shown in FIG. 5, the obtained sintered oil-impregnated bearing 11 is formed with a rough portion 12 having a large surface opening ratio and a dense portion 13 having a surface opening ratio smaller than that of the rough portion 12. The convex portion and the concave portion formed on the inner surface of the green compact become the dense portion 13 and the rough portion 12, respectively, due to the difference in finishing allowance.

[0022]

[Table 1]

Table 1 shows the results obtained by experimentally determining the surface aperture ratio and the number of pores of Samples 1 and 2 before and after finishing. The surface aperture ratios of Samples 1 and 2 were almost the same before finishing, but the surface aperture ratio of Sample 1 after finishing was reduced to about half that of Sample 2. Further, in both cases before and after the finishing process, the sample 1 had a porosity about twice as many as the sample 2. From this, it is understood that by finishing the sintered compact of the green compact formed using the method of the present embodiment, the surface aperture ratio can be made smaller than that of the conventional method. In addition, the green compact formed by the method of the present embodiment originally has many fine porous particles as compared with the green compact formed by the conventional method, and plastic deformation during finishing after sintering is performed. As a result, the fine pores are easily crushed, so that the surface aperture ratio tends to be small.

This is also apparent from the micrographs of the surface state of the green compact shown in FIGS. Here, FIGS. 6 and 7 show the surface state of the green compact before finishing of Samples 2 and 1, respectively, and FIGS. 8 and 9 show the sample 2 after finishing, respectively.
And the surface condition of 1 are shown. From this, it is clear that before and after the finishing process, the sample 2 has a large number of large pores as compared with the sample 1.

According to the present embodiment, by increasing the springback amount, the undercut amount of the green compact defined by the following equation to the inner peripheral surface is 0.7% of the diameter of the inner peripheral surface.
It is possible to increase to a certain degree. Undercut amount ≤ Springback amount + Elastic deformation amount of green compact By this, it is possible to increase the difference in surface aperture ratio between the rough portion and the dense portion of the inner peripheral surface due to the finishing process, so the shape of the undercut Accordingly, it becomes easy to change the surface aperture ratio. Therefore, it is possible to obtain a bearing that can handle a wide range of rotation speeds. Further, high dimensional accuracy with respect to the undercut amount of the core rod becomes unnecessary, and a cheaper core rod can be used.

Since the bearing obtained by the manufacturing method of the present embodiment has the rough portion and the dense portion arranged in the circumferential direction of the inner peripheral surface, the oil from the rough portion to the dense portion can be prevented. It is easy to supply and can be suitably used for bearings for motors in a wide rotation speed range for capstan motors and spindle motors.

Further, since it is possible to reduce or cancel the friction at the time of pulling out the core rod, it is possible to prevent the fine porous particles on the inner peripheral surface of the green compact from being moved and aggregated to form a large porous material. As a result, the surface aperture ratio of the inner peripheral surface can be made smaller on average than in the conventional case, and the formation of the oil film on the sliding surface can be stabilized. In addition, since oil escape can be prevented, metal contact is reduced,
When the shaft is subjected to lateral pressure, it also has the effect of shortening the time required for running in.

Embodiment 2. FIG. 10 shows the second embodiment.
FIG. 3 is a schematic cross-sectional view showing the manufacturing process of the green compact in FIG. Embodiment except that a stepped die is used as the die and a core rod having an undercut in which annular recesses and protrusions of a predetermined width are alternately arranged in the axial direction of the outer peripheral surface shown in FIG. 11 is used. A sintered oil-impregnated bearing can be formed by the same method as in No. 1.

According to the present embodiment, as shown in FIG. 12, a sintered oil-impregnated bearing in which a plurality of rough portions 12 and dense portions 13 having a predetermined width are alternately arranged in an annular direction in the axial direction of the inner peripheral surface is provided. Can be made. Also in this embodiment, the same effect as that of the first embodiment is obtained. That is, since the difference in the surface aperture ratio between the rough portion and the dense portion of the inner peripheral surface due to the finishing process can be increased, it becomes easy to change the surface aperture ratio according to the shape of the undercut. Further, high dimensional accuracy with respect to the undercut amount of the core rod becomes unnecessary, and a cheaper core rod can be used. Further, it is easy to supply and circulate oil from the rough portion to the dense portion, and it can be suitably used as a bearing for a motor of a capstan motor or a spindle motor in a wide rotation speed range. Further, as compared with the conventional case, the formation of an oil film on the sliding surface can be stabilized, and the escape of oil can be prevented, so that metal contact is reduced, and when the shaft receives lateral pressure, the time required for running-in can be shortened.

Further, according to the present invention, since the undercut amount of the core rod can be made large, any shape can be formed as long as it can be processed into a core rod. As a result, in addition to the undercut shapes shown in the first and second embodiments, various shapes of undercut can be provided to the bearing. The modification shown below is a modification of the first embodiment, and is manufactured by the same method as that of the first embodiment except that the shape of the undercut of the core rod is different, and the same effect as that of the first embodiment. Is shown.

That is, in any of the modifications of the first embodiment described below, the difference in the surface aperture ratio between the rough portion and the dense portion of the inner peripheral surface due to the finishing process can be increased, so that the undercut It becomes easy to change the surface aperture ratio according to the shape of the. Further, high dimensional accuracy with respect to the undercut amount of the core rod becomes unnecessary, and a cheaper core rod can be used. Further, it is easy to supply and circulate oil from the rough portion to the dense portion, and it can be suitably used as a bearing for a motor of a capstan motor or a spindle motor in a wide rotation speed range. In addition, compared to the past, it is possible to stabilize the formation of an oil film on the sliding surface,
Since the escape of oil can be prevented, metal contact is reduced, and when the shaft is subjected to lateral pressure, the time required for running-in can be shortened.

Modification 1. FIG. 13 is a schematic plan view showing the shape of the core rod used, and has a shape in which the groove portions 14 and the ridge portions 15 are alternately arranged in the longitudinal direction. FIG. 14A is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using the core rod.
And dense portions 13 are alternately arranged in a grid pattern in the circumferential direction. Further, FIG. 14B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using a core rod in which the concave groove portion 14 and the convex ridge portion 15 of the core rod shown in FIG. 13 are reversed.

Modification 2. The core rod shown in FIG. 11 was used. As shown in the schematic cross-sectional view of FIG. 15A, it has a shape in which annular rough portions 12 and dense portions 13 are alternately arranged in the circumferential direction. In addition, FIG.
FIG. 3 is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing produced by using a core rod in which the concave groove portion 14 and the convex stripe portion 15 of the core rod shown in 1 are reversed.

Modification 3. FIG. 16 is a schematic plan view showing the shape of the core rod used, which has a shape in which a narrow groove portion 14 is arranged at the peripheral portion in the width direction and a wide ridge portion 15 is arranged at the center portion. . FIG. 17 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing produced by using the core rod, in which a narrow annular rough portion 12 is provided at the peripheral portion in the axial direction and a wide annular portion is provided at the central portion. It has a shape in which the dense portion 13 is arranged. 17B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using a core rod in which the concave groove portion 14 and the convex stripe portion 15 of the core rod shown in FIG. 16 are reversed.

Modification 4. FIG. 18 is a schematic plan view showing the shape of the core rod used, which has concave groove portions 14 and convex stripe portions 15 that are oblique and are alternately arranged in the longitudinal direction. FIG. 19 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using the core rod, in which the rough portion 1 is inclined.
2 and the dense portion 13 have a shape in which they are alternately arranged in the circumferential direction. 19B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using a core rod in which the concave groove portion 14 and the convex streak portion 15 of the core rod shown in FIG. 18 are reversed.

Modification 5 FIG. 20 is a schematic plan view showing the shape of the core rod used, and the rectangular recesses 14 are arranged at predetermined intervals so as to be staggered in the longitudinal direction and the width direction. FIG. 21 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using the core rod, and the rectangular dense portions 13 are spaced by a predetermined distance so that they are staggered in the circumferential direction and the width direction. It has a shape that is arranged. 21B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using the core rod in which the concave portion 14 and the convex portion 15 of the core rod shown in FIG. 20 are reversed.

Modification 6. FIG. 22 is a schematic plan view showing the shape of the core rod used, and the diamond-shaped recesses 14 are arranged at predetermined intervals so as to be staggered in the longitudinal direction and the width direction. FIG. 23 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing produced by using the core rod, and the rectangular dense portions 13 are spaced by a predetermined distance so as to alternate in the circumferential direction and the axial direction. It has a shape that is arranged. Also, FIG. 23B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using a core rod in which the concave portions 14 and the convex portions 15 of the core rod shown in FIG. 22 are reversed.

Modified Example 7. FIG. 24 is a schematic plan view showing the shape of the core rod used, in which V-shaped concave groove portions 14 and V-shaped convex streak portions 15 are alternately arranged in the longitudinal direction. FIG. 25 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using the core rod, in which V-shaped rough portions 12 and V-shaped dense portions 13 alternate in the circumferential direction. It has a shape arranged in. Further, FIG. 25 (b)
Is the concave groove portion 14 and the ridge portion 1 of the core rod shown in FIG.
It is a schematic cross section which shows the structure of the sintered oil-impregnated bearing produced using the core rod which reversed 5.

Modified Example 8. FIG. 26 is a schematic plan view showing the shape of the core rod used, in which the concave groove portion 14 including the peripheral edge concave groove portion in the width direction and the zigzag concave groove portion extending in the width direction is arranged in the longitudinal direction. FIG. 27 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing produced by using the core rod, and shows a dense portion 13 composed of a zigzag dense portion and a peripheral dense portion extending in the axial direction, and a surrounding portion thereof. The rough portion 12 and the rough portion 12 are arranged in the circumferential direction. In addition, FIG.
FIG. 27B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using a core rod in which the concave groove portions 14 and the convex portions 15 of the core rod shown in FIG. 26 are reversed.

Modification 9 FIG. 28 is a schematic plan view showing the shape of the core rod used, and it is arranged in a zigzag recessed portion that obliquely extends along the widthwise peripheral recessed groove portion and extends in the longitudinal direction, and in a central portion between the zigzag recessed portion and the peripheral recessed groove portion. A recess 14 composed of a diamond-shaped recess is arranged in the longitudinal direction. FIG. 29
(A) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing produced by using the core rod, and shows a peripheral peripheral dense portion in the axial direction, a zigzag dense portion that obliquely extends in the longitudinal direction, and a zigzag dense portion. And a dense part 13 composed of a diamond-shaped dense part arranged in the central part between the dense part 1 and the peripheral dense part, and a dense part 1 around the dense part 13.
2 and. In addition, FIG. 29 (b) corresponds to FIG.
9 is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using a core rod in which the concave portions 14 and the convex portions 15 of the core rod shown in FIG. 8 are reversed.

Modification 10 FIG. 30 is a schematic plan view showing the shape of the core rod used, and has a W-shaped concave groove portion 14 arranged in the longitudinal direction. FIG. 31 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured by using the core rod, and the W-shaped dense portions 13 and the dense portions 13 are alternately arranged in the circumferential direction. It has a rough portion 12 composed of a W-shaped convex rough portion and a peripheral rough portion in the axial direction. Further, FIG. 31B is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using a core rod in which the concave groove portions 14 and the convex portions 15 of the core rod shown in FIG. 30 are reversed.

Modified Example 11. FIG. 32 is a schematic plan view showing the shape of the core rod used, in which a plurality of concave grooves intersecting with each other in the width direction in an X-shape and connected in the longitudinal direction, a diamond-shaped concave portion arranged in the central portion between the concave grooves, and a peripheral edge It has a concave portion 14 formed of a triangular concave portion arranged along the portion. FIG. 33 (a) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing produced by using the core rod, and shows an X-shaped dense portion intersecting in the X-direction in the width direction and connected in the longitudinal direction, and an X-shape. It has a dense portion 13 composed of a rhombic dense portion arranged in the central portion between the rough portions, a triangular dense portion arranged along the peripheral portion, and a rough portion 12 around the dense portion 13. 33 (b) is a schematic cross-sectional view showing the structure of a sintered oil-impregnated bearing manufactured using a core rod in which the concave portions 14 and the convex portions 15 of the core rod shown in FIG. 32 are reversed.

[0043]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1. 2. An inner diameter having an undercut shape shown in FIG. 5, which is manufactured by using the manufacturing method of the present invention.
The bearing of 5mmφ is installed in the capstan motor, and 60
The change in shaft loss (motor current consumption value) was measured under the conditions of ° C and 10 rpm.

Comparative Example 1. Example 1 except that a bearing having no undercut manufactured by a conventional manufacturing method was used.
In the same manner as above, the bearing was incorporated into the capstan motor and the change in shaft loss was measured.

FIG. 34 shows the results of Example 1 and Comparative Example 1.
It is a graph which shows the relationship between time and the shaft loss of a capstan motor. The bearing of Example 1 is different from the bearing of Comparative Example 1 in
In a short time after the start of rotation, the shaft loss was reduced and the fitting was fast, and the rotational load of the shaft was reduced by about 30%, and the lubricating properties were good.

Example 2. 1. An inner diameter having an undercut shape shown in FIG. 5, which is manufactured by using the manufacturing method of the present invention.
The bearing of 5mmφ is installed in the spindle motor, and 60
The change in axial loss was measured under conditions of 10000 rpm and 10,000 rpm.

Comparative Example 2. Example 2 except that a bearing having no undercut manufactured by a conventional manufacturing method was used.
Similarly to the above, the bearing was incorporated into the spindle motor and the change in the shaft loss was measured.

FIG. 35 shows the results of Example 2 and Comparative Example 2.
It is a graph which shows the relationship between time and the shaft loss of a spindle motor. The bearing of Example 2 is more familiar than the bearing of Comparative Example 2 and the rotational load of the shaft is reduced by about 20%,
It had good lubricating properties.

[0050]

As described above, according to the method for manufacturing a sintered oil-impregnated bearing of the present invention, during the production of a green compact, the green compact is kept pressed by the upper punch and the lower punch. , The core rod and the upper punch and the lower punch are synchronously moved in the axial direction and extracted from the die to release the compression force from the die to the green compact, and the spring back is used to extract the core rod from the green compact. As a result, the amount of springback can be increased and the amount of undercut can be increased compared to the conventional case, and it becomes easy to change the surface aperture ratio according to the shape of the undercut, and the bearing can be used in a wide range of rotational speeds. The production cost can be reduced.

Further, according to the manufacturing method of the present invention, after the green compact having the concave portion and the convex portion formed is sintered, the inner peripheral surface of the sintered body is finished into a perfect circular shape so that the inner peripheral surface has a convex shape. Since a dense part with a small surface opening ratio is formed in the part and an oil passage corresponding to a rough part with a larger surface opening ratio than the dense part is formed in the concave part, the oil supply from the rough part to the dense part and the oil circulation Can be facilitated and the lubrication characteristics can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a step of molding a green compact in a manufacturing method according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a tip shape of a core rod used in the first embodiment of the present invention, where (a) shows a case having a convex portion and (b) shows a case having a concave portion.

FIG. 3 is a graph showing the relationship between the springback ratio and the relative density of the green compact used in the present invention.

FIG. 4 is a schematic diagram showing a finishing step of the manufacturing method according to the first embodiment of the present invention, in which (a) is a schematic side view,
(B) is the roundness of the sintered body before finishing, and (c) is the roundness of the sintered body after finishing.

FIG. 5 is a schematic cross-sectional view showing the structure of a bearing manufactured by using the manufacturing method according to the first embodiment of the present invention.

FIG. 6 is a micrograph showing a surface state of a sintered compact of a green compact molded by a conventional manufacturing method before a finishing step.

FIG. 7 is a micrograph showing a surface state of a green compact sintered body molded by the manufacturing method according to the first embodiment of the present invention before a finishing step.

FIG. 8 is a micrograph showing a surface condition of a sintered compact of a green compact which has been molded by a conventional manufacturing method, after a finishing step.

FIG. 9 is a micrograph showing a surface condition of a sintered compact of a green compact molded by the manufacturing method according to the first embodiment of the present invention after a finishing step.

FIG. 10 is a schematic cross-sectional view showing a step of molding a green compact in the manufacturing method according to the second embodiment of the present invention.

FIG. 11 is a schematic plan view showing the tip shape of the core rod used in the manufacturing method according to the second embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view showing the structure of a bearing manufactured by the manufacturing method according to the second embodiment of the present invention.

FIG. 13 is a schematic plan view showing the shape of the core rod used in the production of the bearing of Modification 1 according to Embodiment 1 of the present invention.

14A and 14B are views showing a structure of a bearing of a modified example 1 according to the first embodiment of the present invention, FIG. 14A is a schematic sectional view of a bearing manufactured by using the core rod shown in FIG. 13, and FIG. FIG. 14 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 13.

15A and 15B are views showing a structure of a bearing of Modification 2 according to the first embodiment of the present invention, FIG. 15A is a schematic cross-sectional view of the bearing manufactured by using the core rod shown in FIG. 11, and FIG. FIG. 12 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 11.

FIG. 16 is a schematic plan view showing the shape of a core rod used for manufacturing the bearing of Modification 3 according to Embodiment 1 of the present invention.

FIG. 17 is a diagram showing the structure of a bearing of Modification 3 according to the first embodiment of the present invention, (a) is a schematic cross-sectional view of a bearing manufactured using the core rod shown in FIG. 16, and (b) is a diagram. FIG. 17 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 16.

FIG. 18 is a schematic plan view showing the shape of a core rod used for manufacturing the bearing of Modification 4 according to Embodiment 1 of the present invention.

FIG. 19 is a diagram showing a structure of a bearing of Modification 4 according to the first embodiment of the present invention, (a) is a schematic cross-sectional view of the bearing manufactured by using the core rod shown in FIG. 18, and (b) is a diagram. FIG. 19 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 18.

FIG. 20 is a schematic plan view showing the shape of a core rod used for manufacturing the bearing of Modification 5 according to Embodiment 1 of the present invention.

21 is a diagram showing the structure of a bearing of Modification 5 according to Embodiment 1 of the present invention, (a) is a schematic cross-sectional view of a bearing manufactured using the core rod shown in FIG. 20, and (b) is a diagram. FIG. 21 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 20.

FIG. 22 is a schematic plan view showing the shape of a core rod used for manufacturing the bearing of Modification 6 according to Embodiment 1 of the present invention.

FIG. 23 is a diagram showing a structure of a bearing of Modification 6 according to the first embodiment of the present invention, (a) is a schematic cross-sectional view of a bearing manufactured by using the core rod shown in FIG. 22, and (b) is a diagram. 23 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG.

FIG. 24 is a schematic plan view showing the shape of a core rod used for manufacturing the bearing of Modification 7 according to Embodiment 1 of the present invention.

FIG. 25 is a diagram showing a structure of a bearing of Modification 7 according to the first embodiment of the present invention, (a) is a schematic cross-sectional view of the bearing manufactured by using the core rod shown in FIG. 24, and (b) is a diagram. FIG. 25 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 24.

FIG. 26 is a schematic plan view showing the shape of the core rod used for manufacturing the bearing of Modification 8 according to Embodiment 1 of the present invention.

27 is a diagram showing the structure of a bearing of Modification 8 according to Embodiment 1 of the present invention, FIG. 27 (a) is a schematic cross-sectional view of a bearing produced using the core rod shown in FIG. 26, and FIG. FIG. 27 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 26.

FIG. 28 is a schematic plan view showing the shape of the core rod used for manufacturing the bearing of Modification 9 according to Embodiment 1 of the present invention.

FIG. 29 is a diagram showing the structure of a bearing of Modification 9 according to the first embodiment of the present invention, (a) is a schematic cross-sectional view of the bearing manufactured using the core rod shown in FIG. 28, and (b) is a diagram. FIG. 29 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 28.

FIG. 30 is a schematic plan view showing the shape of the core rod used for manufacturing the bearing of Modification 10 according to Embodiment 1 of the present invention.

FIG. 31 is a diagram showing the structure of a bearing of Modification 10 according to Embodiment 1 of the present invention, (a) is a schematic cross-sectional view of the bearing manufactured by using the core rod shown in FIG. 30, and (b) is a diagram. ,
FIG. 31 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 30.

FIG. 32 is a schematic plan view showing the shape of a core rod used for manufacturing the bearing of Modification 11 according to Embodiment 1 of the present invention.

FIG. 33 is a diagram showing a structure of a bearing of Modification 11 according to the first embodiment of the present invention, (a) is a schematic cross-sectional view of the bearing manufactured by using the core rod shown in FIG. 32, and (b) is a diagram. ,
FIG. 33 is a schematic cross-sectional view of a bearing manufactured by reversing the concave portion and the convex portion of the core rod shown in FIG. 32.

FIG. 34 is a graph showing a change over time in shaft loss of a capstan motor to which a bearing manufactured using the manufacturing method of the present invention is attached.

FIG. 35 is a graph showing the change over time in the shaft loss of a spindle motor equipped with a bearing manufactured using the manufacturing method of the present invention.

FIG. 36 is a schematic cross-sectional view showing a manufacturing process of a green compact in a conventional manufacturing method.

[Explanation of symbols]

1 raw material powder, 2 powder compact, 3 die, 4 core rod, 5 upper punch, 6 lower punch, 10a, 10b sintered body, 11 bearing, 12 rough part, 13 dense part, 14 core rod recess, 15 core rod protrusion Parts, 16 bearing holders, 17 fixing jigs, 18 rotator chuck parts, 1
9 Finishing tools.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI F16C 33/14 F16C 33/14 A (72) Inventor Takuji Harano 12-32 Taisei-cho, Neyagawa-shi, Osaka Japan Department Gakuin Metallurgical Co., Ltd. (56) References JP-A-11-190344 (JP, A) JP-A-2000-54003 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22F 3/02-3 / 035,5 / 00 B30B 11/00-11/02 F16C 33/14

Claims (2)

(57) [Claims] 1. An outer die, a core rod coaxially arranged in the die and having a plurality of recesses and protrusions on its outer peripheral surface, and a lower punch slidably fitted between the die and the core rod. Sintered oil impregnation in which raw material powder is filled in the voids formed by the above, the lower punch and the upper punch are moved in the axial direction, the raw material powder is pressure-compressed to form a green compact, and then the green compact is sintered. In the method of manufacturing a bearing, while maintaining the pressed state of the green compact by the upper punch and the lower punch, the core rod and the upper punch and the lower punch are synchronously moved in the axial direction and extracted from the die,
While releasing the compressive force from the die to the green compact, the core rod is pulled out from the green compact with the expanded inner diameter by springback, and then the upper punch is removed to form multiple concave and convex parts on the inner peripheral surface. A method for manufacturing a sintered oil-impregnated bearing, comprising forming a green compact having the same. 2. The manufacturing method according to claim 1, further comprising sintering the green compact, finishing the inner peripheral surface into a perfect circle, and projecting the inner peripheral surface into a dense portion having a small surface aperture ratio. The manufacturing method according to claim 1, wherein the concave portion is formed in the rough portion having a surface aperture ratio larger than that of the dense portion.